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Methods for producing heat spreaders utilizing void regions in blanks to selectively accommodate material cold flow

IP.com Disclosure Number: IPCOM000244754D
Publication Date: 2016-Jan-11
Document File: 5 page(s) / 160K

Publishing Venue

The IP.com Prior Art Database

Abstract

In the manufacture of heat spreaders of the type used for semiconductor die packages, extreme material cold flow encountered in shaping complex parts can be accommodated by providing strategically placed recesses or voids in the part blank. These recesses receive material cold flow from regions of the blank that are thinned by punching, coining, and shaping, thereby lowering punch pressures needed to produce heat spreader features of complex geometry. This, in turn, allows for the use of single-gage metallic sheet stock having a uniform thickness for producing parts that would otherwise require more expensive multi-gage metallic sheet stock.

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Methods for producing heat spreaders utilizing void regions in blanks to selectively accommodate material cold flow

Abstract

In the manufacture of heat spreaders of the type used for semiconductor die packages, extreme material cold flow encountered in shaping complex parts can be accommodated by providing strategically placed recesses or voids in the part blank. These recesses receive material cold flow from regions of the blank that are thinned by punching, coining, and shaping, thereby lowering punch pressures needed to produce heat spreader features of complex geometry. This, in turn, allows for the use of single-gage metallic sheet stock having a uniform thickness for producing parts that would otherwise require more expensive multi-gage metallic sheet stock.

Background

Heat spreaders are used in semiconductor die or computer chip packages, such as the package shown schematically in Figure 1 below, to conduct heat away from a computer chip or semiconductor die 1, which is typically secured to a substrate such as a PCB 2. The heat spreader 3 conducts heat from the die 1 to a heat sink 4 for dissipation into the surrounding ambient environment. Typically, a first thermal interface material (TIM) 5 is used between the die and the heat spreader and a second thermal interface material (TIM) 6 is used between the heat spreader and the heat sink.

The heat spreader is typically made of a highly heat conductive metal or metal alloy such as pure copper or aluminum, or a copper alloy or an aluminum alloy, for example. Optionally, the heat spreader may be coated or plated with another heat conductive metal or metal alloy.

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US.103880017.01


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Heat spreaders may be made in large volumes from bulk metal sheet stock by cutting or punching a blank from the sheet or strip and using a combination of punching or coining processes to impart desired shapes and geometrical features to the blank to produce the finished heat spreader. Progressive or transfer dies are typically used.

As shown in Figure 1 above, a heat spreader may be hat-shaped and includes a recess, channel or other cavity which receives the die of the finished package. A peripheral flange may be located around the edges of the cavity to provide an attachment surface for securing the heat spreader to the underlying substrate, such as by adhesive.

During the punching and/or shaping processes used for heat spreader manufacture, material is sometimes not physically removed from the blank but rather flows from areas of high tool contact pressure to areas of lower tool contact pressure, such as from within a periphery of a punch outwardly beyond the punch periphery. This material flow is referred to as "cold flow".

For heat spreader shapes having more complex geometries, the ability for relatively large volumes of material to flow from one location to another may be a limiting factor. In the past, some complex parts have required procurement of sheet stock having a non-uniform...